(a) Field of the Invention
The present invention related to a hydraulic circuit with a cooling device including mainly two hydraulic cylinders, a cooling device in the form of a rectangular structure having two oil channels each for connecting to a hydraulic cylinder and a spare tiny passage to keep on connecting to the oil channels, a control valve to close and open the oil channels, a plurality of cooling fins formed perpendicular to a side of the cooling device, and a fan for fast cooling effect whereby the hydraulic cylinders can be driven for reciprocating movements in two opposite directions with controllable load for use in, for example, exercise equipment such as walking exercise machine, boat rower, or indoor bicycle.
(b) Description of the Prior Art
Conventionally each exercise equipment, such as walking exercise machine, boat rower, or indoor bicycle, uses two hydraulic cylinders connecting to pedals or oars to provide load for stepping or rowing by a control on hydraulic load. However, for each adjustment of hydraulic load, the hydraulic cylinders must be adjusted respectively. Moreover, the frequent operation of pistons results in rising of hydraulic oil temperature and consequently damages oil seals, and forcefully stepping or rowing without prior adjustment when their control valves are closed will result in damage to the hydraulic cylinders.